In the Framingham Heart Study, about 22 percent of men aged 65 and older and 15 percent of women lost 5 percent or more of body weight. To investigate the relationship of weight change to change in body composition in this older cohort, we entered into an agreement to obtain body composition measurements with dual energy x-ray absorptiometry (DEXA) for muscle, bone and body fat as well as to obtain reasons for weight change. This study began in December of 1993.